A Launceston angler’s unexpected catch has triggered an extensive fisheries survey, after a redfin perch turned up in a lake where the invasive species wasn’t supposed to exist.
Logan Reid was fishing at Four Springs Lake in late April when he landed the 410-millimetre fish weighing 1.4 kilograms – a catch that immediately raised alarm bells with the Inland Fisheries Service (IFS).
The discovery prompted an urgent two-day survey in early May, with fisheries officers deploying boat electrofishing equipment, 30 box traps and 12 fine mesh fyke nets across the lake.
Despite hours of work, the team found thousands of smelt, brown and rainbow trout and short-finned eels – but not a single other redfin perch.
Lab tests revealed the caught fish was a nine-year-old mature female carrying 95 grams of eggs, suggesting it had been living undetected in the lake for years.
IFS researchers, working with IMAS scientist Pete Coulson, who aged the fish using its ear bones, believe it was a lone arrival rather than evidence of an established population.
“While the source of the single fish is unknown, the survey results and size/age of the fish suggest this capture is a one-off that entered the lake a long time ago and has managed to avoid capture since,” the IFS said.
The IFS noted that years of previous surveys and heavy angling pressure at the popular fishing spot had never turned up a redfin perch until now.
Still, fisheries officials aren’t taking any chances. More monitoring is on the way, including an environmental DNA survey.
Anglers have also been urged to stay alert when the new brown trout season opens in August.
Redfin perch are considered a serious threat to Tasmania’s freshwater ecosystems.
Introduced in the 1860s, the aggressive species breeds quickly and can overrun waterways, putting native fish and trout populations at risk.
